https://github.com/lenary updated https://github.com/llvm/llvm-project/pull/163666
>From 132e1d6b631c61b643fb02cd2d3c50c09e880d09 Mon Sep 17 00:00:00 2001 From: Sam Elliott <[email protected]> Date: Wed, 15 Oct 2025 17:26:19 -0700 Subject: [PATCH 1/3] [clang] Add clang::nooutline Attribute This change: - Adds a `[[clang::nooutline]]` function attribute for C and C++. There is no equivalent GNU syntax for this attribute, so no `__attribute__` syntax. - Uses the presence of `[[clang::nooutline]]` to add the `nooutline` attribute to IR function definitions. - Adds test for the above. The `nooutline` attribute disables both the Machine Outliner (enabled at Oz for some targets), and the IR Outliner (disabled by default). --- clang/include/clang/Basic/Attr.td | 7 +++++++ clang/lib/CodeGen/CodeGenModule.cpp | 3 +++ clang/test/CodeGen/attr-nooutline.c | 16 ++++++++++++++++ ...agma-attribute-supported-attributes-list.test | 1 + clang/test/Sema/attr-nooutline.c | 7 +++++++ clang/test/Sema/attr-nooutline.cpp | 7 +++++++ 6 files changed, 41 insertions(+) create mode 100644 clang/test/CodeGen/attr-nooutline.c create mode 100644 clang/test/Sema/attr-nooutline.c create mode 100644 clang/test/Sema/attr-nooutline.cpp diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td index 22e60aa9fe312..b8a61ba4cbac9 100644 --- a/clang/include/clang/Basic/Attr.td +++ b/clang/include/clang/Basic/Attr.td @@ -2355,6 +2355,13 @@ def NoInline : DeclOrStmtAttr { let SimpleHandler = 1; } +def NoOutline : DeclOrStmtAttr { + let Spellings = [CXX11<"clang", "nooutline">, C23<"clang", "nooutline">]; + let Subjects = SubjectList<[Function], ErrorDiag>; + let Documentation = [Undocumented]; + let SimpleHandler = 1; +} + def NoMips16 : InheritableAttr, TargetSpecificAttr<TargetMips32> { let Spellings = [GCC<"nomips16">]; let Subjects = SubjectList<[Function], ErrorDiag>; diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index 8d019d4b2da25..ab267236ed579 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -2820,6 +2820,9 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D, B.addAttribute(llvm::Attribute::MinSize); } + if (D->hasAttr<NoOutlineAttr>()) + B.addAttribute(llvm::Attribute::NoOutline); + F->addFnAttrs(B); unsigned alignment = D->getMaxAlignment() / Context.getCharWidth(); diff --git a/clang/test/CodeGen/attr-nooutline.c b/clang/test/CodeGen/attr-nooutline.c new file mode 100644 index 0000000000000..b9f175da24cb5 --- /dev/null +++ b/clang/test/CodeGen/attr-nooutline.c @@ -0,0 +1,16 @@ +// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --check-attributes --version 6 +// RUN: %clang_cc1 -emit-llvm %s -triple x86_64-unknown-linux-gnu -disable-O0-optnone -o - | FileCheck %s + + +// CHECK: Function Attrs: noinline nooutline nounwind +// CHECK-LABEL: define dso_local i32 @t1( +// CHECK-SAME: i32 noundef [[X:%.*]]) #[[ATTR0:[0-9]+]] { +// CHECK-NEXT: [[ENTRY:.*:]] +// CHECK-NEXT: [[X_ADDR:%.*]] = alloca i32, align 4 +// CHECK-NEXT: store i32 [[X]], ptr [[X_ADDR]], align 4 +// CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[X_ADDR]], align 4 +// CHECK-NEXT: ret i32 [[TMP0]] +// +[[clang::nooutline]] int t1(int x) { + return x; +} diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test index 73d4cb1769ed5..7ef758dbea9eb 100644 --- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test +++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test @@ -123,6 +123,7 @@ // CHECK-NEXT: NoMerge (SubjectMatchRule_function, SubjectMatchRule_variable) // CHECK-NEXT: NoMicroMips (SubjectMatchRule_function) // CHECK-NEXT: NoMips16 (SubjectMatchRule_function) +// CHECK-NEXT: NoOutline (SubjectMatchRule_function) // CHECK-NEXT: NoProfileFunction (SubjectMatchRule_function) // CHECK-NEXT: NoRandomizeLayout (SubjectMatchRule_record) // CHECK-NEXT: NoSanitize (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_variable_is_global) diff --git a/clang/test/Sema/attr-nooutline.c b/clang/test/Sema/attr-nooutline.c new file mode 100644 index 0000000000000..83848c22d1003 --- /dev/null +++ b/clang/test/Sema/attr-nooutline.c @@ -0,0 +1,7 @@ +// RUN: %clang_cc1 %s -verify -fsyntax-only + +[[clang::nooutline]] int a; // expected-error {{'clang::nooutline' attribute only applies to functions}} + +[[clang::nooutline]] void t1(void); + +[[clang::nooutline(2)]] void t2(void); // expected-error {{'clang::nooutline' attribute takes no arguments}} diff --git a/clang/test/Sema/attr-nooutline.cpp b/clang/test/Sema/attr-nooutline.cpp new file mode 100644 index 0000000000000..b6c9b3995081a --- /dev/null +++ b/clang/test/Sema/attr-nooutline.cpp @@ -0,0 +1,7 @@ +// RUN: %clang_cc1 -verify -fsyntax-only %s -Wno-c++17-extensions + +[[clang::nooutline]] int a; // expected-error {{'clang::nooutline' attribute only applies to functions}} + +[[clang::nooutline]] void t1(void); + +[[clang::nooutline(2)]] void t2(void); // expected-error {{'clang::nooutline' attribute takes no arguments}} >From 6337dd0419d4af9d83273f4024bd206f29e4f817 Mon Sep 17 00:00:00 2001 From: Sam Elliott <[email protected]> Date: Thu, 16 Oct 2025 13:25:32 -0700 Subject: [PATCH 2/3] Address reviewer feedback: Tests, Docs, TableGen --- clang/include/clang/Basic/Attr.td | 4 ++-- clang/include/clang/Basic/AttrDocs.td | 30 +++++++++++++++++++++++++++ clang/test/CodeGen/attr-nooutline.c | 29 +++++++++++++++++--------- 3 files changed, 51 insertions(+), 12 deletions(-) diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td index b8a61ba4cbac9..5d12dda3740bc 100644 --- a/clang/include/clang/Basic/Attr.td +++ b/clang/include/clang/Basic/Attr.td @@ -2356,9 +2356,9 @@ def NoInline : DeclOrStmtAttr { } def NoOutline : DeclOrStmtAttr { - let Spellings = [CXX11<"clang", "nooutline">, C23<"clang", "nooutline">]; + let Spellings = [Clang<"nooutline">]; let Subjects = SubjectList<[Function], ErrorDiag>; - let Documentation = [Undocumented]; + let Documentation = [NoOutlineDocs]; let SimpleHandler = 1; } diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td index e0bbda083b5cf..2ece34542a952 100644 --- a/clang/include/clang/Basic/AttrDocs.td +++ b/clang/include/clang/Basic/AttrDocs.td @@ -862,6 +862,36 @@ with ``__noinline__`` defined as a macro as ``__attribute__((noinline))``. }]; } +def NoOutlineDocs : Documentation { + let Category = DocCatFunction; + let Content = [{ +This function attribute suppresses outlining from the annotated function. + +Outlining is the process where common parts of separate functions are extracted +into a separate function (or assembly snippet), and calls to that function or +snippet are inserted in the original functions. In this way, it can be seen as +the opposite of inlining. It can help to reduce code size. + +.. code-block:: c + + [[clang::nooutline]] int x1(int y) { + int z = COMPLEX_MACRO(y); // Not outlined + return z + const1; + } + + int x2(int y) { + int z = COMPLEX_MACRO(y); // May be outlined + return z * const2; + } + + int x3(int y) { + int z = COMPLEX_MACRO(y); // May be outlined + reutrn z / const3; + } + + }]; +} + def MustTailDocs : Documentation { let Category = DocCatStmt; let Content = [{ diff --git a/clang/test/CodeGen/attr-nooutline.c b/clang/test/CodeGen/attr-nooutline.c index b9f175da24cb5..8519414397a8b 100644 --- a/clang/test/CodeGen/attr-nooutline.c +++ b/clang/test/CodeGen/attr-nooutline.c @@ -1,15 +1,24 @@ // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --check-attributes --version 6 -// RUN: %clang_cc1 -emit-llvm %s -triple x86_64-unknown-linux-gnu -disable-O0-optnone -o - | FileCheck %s +// RUN: %clang_cc1 -emit-llvm %s -triple x86_64-unknown-linux-gnu -o - | FileCheck %s --check-prefix=C +// RUN: %clang_cc1 -emit-llvm -x c++ %s -triple x86_64-unknown-linux-gnu -o - | FileCheck %s --check-prefix=CXX - -// CHECK: Function Attrs: noinline nooutline nounwind -// CHECK-LABEL: define dso_local i32 @t1( -// CHECK-SAME: i32 noundef [[X:%.*]]) #[[ATTR0:[0-9]+]] { -// CHECK-NEXT: [[ENTRY:.*:]] -// CHECK-NEXT: [[X_ADDR:%.*]] = alloca i32, align 4 -// CHECK-NEXT: store i32 [[X]], ptr [[X_ADDR]], align 4 -// CHECK-NEXT: [[TMP0:%.*]] = load i32, ptr [[X_ADDR]], align 4 -// CHECK-NEXT: ret i32 [[TMP0]] +// C: Function Attrs: noinline nooutline nounwind optnone +// C-LABEL: define dso_local i32 @t1( +// C-SAME: i32 noundef [[X:%.*]]) #[[ATTR0:[0-9]+]] { +// C-NEXT: [[ENTRY:.*:]] +// C-NEXT: [[X_ADDR:%.*]] = alloca i32, align 4 +// C-NEXT: store i32 [[X]], ptr [[X_ADDR]], align 4 +// C-NEXT: [[TMP0:%.*]] = load i32, ptr [[X_ADDR]], align 4 +// C-NEXT: ret i32 [[TMP0]] +// +// CXX: Function Attrs: mustprogress noinline nooutline nounwind optnone +// CXX-LABEL: define dso_local noundef i32 @_Z2t1i( +// CXX-SAME: i32 noundef [[X:%.*]]) #[[ATTR0:[0-9]+]] { +// CXX-NEXT: [[ENTRY:.*:]] +// CXX-NEXT: [[X_ADDR:%.*]] = alloca i32, align 4 +// CXX-NEXT: store i32 [[X]], ptr [[X_ADDR]], align 4 +// CXX-NEXT: [[TMP0:%.*]] = load i32, ptr [[X_ADDR]], align 4 +// CXX-NEXT: ret i32 [[TMP0]] // [[clang::nooutline]] int t1(int x) { return x; >From a729b26164df976c11093d05ac6bebda947e75cc Mon Sep 17 00:00:00 2001 From: Sam Elliott <[email protected]> Date: Thu, 16 Oct 2025 13:46:36 -0700 Subject: [PATCH 3/3] Release Notes --- clang/docs/ReleaseNotes.rst | 3 +++ 1 file changed, 3 insertions(+) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 6ebc2f0f63fa7..618ab1855887f 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -269,6 +269,9 @@ Non-comprehensive list of changes in this release allocation functions with a token ID can be enabled via the ``-fsanitize=alloc-token`` flag. +- Added a new attribute, ``[[clang::nooutline]]`` to suppress outlining from + annotated functions. This uses the LLVM `nooutline` attribute. + New Compiler Flags ------------------ - New option ``-fno-sanitize-debug-trap-reasons`` added to disable emitting trap reasons into the debug info when compiling with trapping UBSan (e.g. ``-fsanitize-trap=undefined``). _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
